Security readout for executives and security teams
Plain-English summary
Synology Calendar had an authorization flaw that could let a logged-in remote user create calendar events where they should not be allowed. This is not described as unauthenticated or actively exploited, but it can still affect shared calendars, operational schedules, and trust in calendar data.
Executive priority
Prioritize remediation for internet-accessible or multi-user Synology Calendar systems. Treat as moderate urgency: it is authenticated and limited impact, but unauthorized schedule changes can disrupt teams and operations.
Technical view
CVE-2018-8927 is CWE-863 in SYNO.Cal.Event in Synology Calendar before 2.1.2-0511. A remote authenticated user could create arbitrary events through cal_id or original_cal_id handling. CVSS 3.0 is 5.4, with network access, low complexity, low privileges, no user interaction, and limited integrity and availability impact.
Likely exposure
Exposure is limited to Synology Calendar deployments running versions before 2.1.2-0511 where untrusted or lower-privileged users can authenticate remotely.
Exploitation context
The provided sources do not show CISA KEV listing or confirmed active exploitation. Exploitation requires authentication, which lowers broad internet risk but still matters in multi-user NAS or externally reachable Calendar environments.
Researcher notes
The public detail is concise. The vulnerable surface is SYNO.Cal.Event parameter authorization around cal_id and original_cal_id. Avoid assuming broader Synology products are affected unless vendor data confirms it.
Mitigation direction
- Upgrade Synology Calendar to 2.1.2-0511 or later.
- Check Synology’s advisory for any product-specific guidance.
- Restrict remote Calendar access to trusted users and networks.
- Review calendar permissions for low-privileged or stale accounts.
Validation and detection
- Inventory Synology Calendar versions across NAS assets.
- Confirm no instance runs Calendar before 2.1.2-0511.
- Review logs for unexpected event creation by low-privileged users.
- Verify shared calendar permissions match business need.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-863: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2018-8927 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.4 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L2.82.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
5.4MediumVector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://www.synology.com/en-global/support/security/Synology_SA_18_16CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Incorrect Authorization
Incorrect Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.